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Biomedical subjects

F Felici

Publications and source records attributed to F Felici.

At least 19 recordsLinked to original sources
PubMed2006

The cannabinoid receptor agonist WIN 55,212-2 attenuates the effects induced by quinolinic acid in the rat striatum.

The ability of CB(1) receptors to regulate the release of glutamate in the striatum, together with the finding that, in experimental models of Huntington disease (HD), both endocannabinoid levels and CB(1) receptor densities are reduced, has prompted the investigation on the neuroprotective role of the cannabinoids in HD. Quinolinic acid (QA) is an excitotoxin that, when injected in the rat striatum reproduces many features of HD and that acts by stimulating glutamate outflow. The aim of the present study was to test the ability of the cannabinoid receptor agonist WIN 55,212-2 to prevent the effects induced by QA in the rat striatum. In microdialysis experiments, probe perfusion with WIN 55,212-2 significantly and dose-dependently prevented the increase in extracellular glutamate induced by QA. In electrophysiological recordings in corticostriatal slices, the application of WIN 55,212-2 prevented QA-induced reduction of the field potential amplitude. Both effects of WIN 55,212-2 were prevented by the CB(1) receptor antagonist AM 251. In in vivo experiments, intrastriatal WIN 55,212-2 significantly attenuated the striatal damage induced by QA, although no significant effects were observed on a behavioural ground. These data demonstrate that the stimulation of CB(1) receptors might lead to neuroprotective effects against excitotoxic striatal toxicity.

Animals↗
PubMed2004

Influence of high motor unit synchronization levels on non-linear and spectral variables of the surface EMG.

The aim of this study was to investigate the influence of high degrees of motor unit synchronization on surface EMG variables extracted by linear and non-linear analysis techniques. For this purpose, spectral and recurrent quantification analysis (RQA) were applied to both simulated and experimental EMG signals. Synthetic surface EMG signals were generated with a model of volume conductor comprising muscle, fat, and skin tissues. The synchronization was quantified by the percent of discharges of each motor unit synchronized with discharges of other motor units. The simulated signals presented degrees of synchronization in the range 0-80% (10% increments) and three mean values of motor unit conduction velocity distribution (3, 4 and 5 m/s). Experimental signals were collected from the first dorsal interosseous muscle of five patients with Parkinson disease during 10s of rest and 10s of isometric voluntary contraction at 50% of the maximal force. Mean power spectral frequency (MNF) and percent of determinism (%DET) of the surface EMG were computed from the simulated and experimental signals. In the simulated signals, %DET was linearly related to the level of synchronization in the entire range considered while MNF was sensitive to changes in synchronization in a smaller range (0-20%), outside which it levelled off. The experimental results indicated that %DET was significantly higher in the resting condition (with presence of tremor; mean +/- S.E., 85.4 +/- 0.8%) than during the voluntary contraction (which partly suppressed tremor; 60.0 +/- 2.3%; P < 0.01). On the contrary, MNF did not depend on the condition (114.3 +/- 1.5 Hz and 118.0 +/- 0.8 Hz for the resting and voluntary contraction, respectively), confirming the simulation results. Overall, these results indicated that linear and non-linear analyses of the surface EMG may have different sensitivities to the underlying physiological mechanisms in specific conditions, thus their joint use provides a more complete view of the muscle status than spectral analysis only.

Action Potentials↗
PubMed2003

Amplitude and spectral characteristics of biceps Brachii sEMG depend upon speed of isometric force generation.

In the present study the influence of speed of contraction on the interplay between recruitment and firing rate of motor units (MUs) was assessed. The surface electromyographic (sEMG) signal was recorded in nine healthy subjects from the right biceps brachii using a linear electrode array during ramp isometric contractions (from 0 to 100% of the maximal voluntary force, MVC) at 5, 10, and 20% MVC s(-1) (ramp phase), followed by 10 s of sustained MVC (hold phase). The median frequency (MDF), Root Mean Square (RMS) and conduction velocity (CV) of sEMG, were computed on adjacent epochs covering a force range of 5% MVC each. Full motor unit recruitment (FMUR) point was assessed as the force level at which MDF reached its maximum value; the MDF decay during the hold phase was taken as an index of localized muscle fatigue. At 5% MVC s(-1), FMUR was reached at 52.3% MVC. At 10%MVC s(-1) FMUR was achieved at 58% MVC; while at 20% MVC s(-1) FMUR point was located at 77% MVC, being statistically different from 5 and 10% MVCs(-1) ramps (p<0.05). The MDF decay was steeper at higher speed. CV modifications mirrored those reported for MDF. The RMS increased in a curvilinear fashion and the maximum value was always attained during the hold phase. Our findings suggest that MU recruitment strategies are significantly related to the speed of contraction even in a single muscle.

Adult↗
PubMed2001

Identification of a LFA-1 region involved in the HIV-1-induced syncytia formation through phage-display technology.

We have identified a peptide region on CD18 molecule (the beta subunit of the LFA-1 molecule) involved in syncytia formation of HIV-1-infected lymphocytes. Several phage clones mimicking an epitope of the CD18 cell-surface determinant were isolated from two 9-mer random peptide phage-displayed libraries via their binding to the CD18-specific monoclonal antibody (mAb) MHM23, which in in vitro assay inhibits syncytia formation in HIV-1-infected cells. The peptide sequences displayed on phages that blocked immunolabeling of this mAb on LFA-1-expressing cells were used to identify the epitope recognized by mAb MHM23 by sequence comparison. On the basis of this analysis, two peptides which inhibited syncytia formation in HIV-1-infected cells in vitro were synthesized, thus confirming that they mimic a CD18 domain that is involved in this phenomenon. The results here presented highlight the potential of phage-display technology for the study of biological processes at the basis of virus infection, but also suggest new approaches for the therapy of AIDS.

Animals↗
PubMed2001

Linear and non-linear analysis of surface electromyograms in weightlifters.

The present research was aimed at investigating the peculiarities of surface electromyogram (sEMG) signals in 12 weightlifting athletes (WLA) and 9 control subjects (control group, CG) The sEMG signals were recorded from both vastus lateralis muscles during 20 s isometric contractions made at 30% and 60% of the maximal voluntary contraction (MVC). Ground reaction force (vertical component) was recorded using a force plate. The sEMG was analysed in the frequency domain and the median frequency (MDF) was computed over successive 1 s epochs. A non-linear technique, recurrence quantification analysis was also applied to assess the presence and time course of deterministic structures in sEMG. The percentage of determinism (%DET) was used as a synthetic parameter to quantify the amount of regularly repeating sEMG waves within the signal itself (bursts). In 5 WLA the sEMG displayed a clear burst activity centred at 11 Hz. These bursts were correlated with force output oscillations and were evident both at 30% and 60% MVC. The MDF decay with time was more evident in WLA than in CG subjects. The %DET increased in WLA, this increase being more evident during 60% MVC contractions. Our results seemed to suggest a special disposition among WLA for the development of long-term changes in firing probability during sub-maximal isometric exercise. The MDF and %DET data provided indications of a greater involvement of fast twitch muscle fibres in WLA than in CG.

Adult↗
PubMed2001

Effect of human exposure to altitude on muscle endurance during isometric contractions.

The aim of this study was to evaluate the influence of exposure to altitude on muscle endurance during isometric contractions. Six sedentary subjects were studied. Surface electromyograph (sEMG) activity was recorded from the right biceps brachii (BB) during exhausting isometric exercise at 80% maximal voluntary contraction. Experiments were performed before, during and 6 months after a 12 day stay at the EV-K2 laboratory (Nepal, 5,050 m above sea level). From the sEMG signals from BB, the median frequencies (fmed) were computed for consecutive 1 s epochs. The sEMG was also analysed using a non-linear tool, the recurrence quantification analysis, and the percentage of determinism (%DET) was then calculated. The haemoglobin saturation significantly decreased at altitude. The mean (SD) BB endurance time decreased from 22.4 (4) s to 18.3 (4.7) s (P < 0.05). After exposure to altitude a significant variation in fmed and %DET slopes was observed. We concluded that during the first period of acclimatisation at altitude there was an impairment of isometric muscle endurance performance and there was also evidence of a modified myoelectric activity pattern suggesting a greater fatigability of the neuromuscular system.

Adult↗
PubMed2001

Identification of a human immunodominant B-cell epitope within the GRA1 antigen of Toxoplasma gondii by phage display of cDNA libraries.

Excreted secreted antigens of the protozoan parasite Toxoplasma gondii play a key role in stimulating the host immune system during acute and chronic infection. With the aim of identifying the immunodominant epitopes of T. gondii antigens involved in the human B-cell response against the parasite, we employed a novel immunological approach. A library of cDNA fragments from T. gondii tachyzoites was displayed as fusion proteins to the amino-terminus of lambda bacteriophage capsid protein D. The lambda D-tachyzoite library was then affinity-selected by using a panel of sera of pregnant women, all infected with the parasite. Some of the clones identified through this procedure matched the sequence of the dense granule GRA1 protein (p24), allowing us to identify its antigenic regions. In particular, the analysis of human antibody response against the recombinant GRA1 antigen fragments revealed the existence of an immunodominant epitope (epi-24 peptide).

Amino Acid Sequence↗
PubMed2001

Exercise induced muscle damage and recovery assessed by means of linear and non-linear sEMG analysis and ultrasonography.

This study was aimed at investigating the time-course and recovery from eccentric (EC) exercise induced muscle damage by means of surface electromyography (sEMG), ultrasonography (US), and blood enzymes. Five subjects (EC Group) performed two bouts of 35 EC maximum contractions with the biceps brachii of their non dominant arm, five subjects were tested without performing EC (Control Group: CNT). The maximal isometric force (MVC) was measured. Force and sEMG signals were recorded during 80% MVC isometric contractions. In EC and CNT subjects US assessment on non-dominant biceps brachii was performed; creatin kinase (CK) and lactic dehydrogenasis (LDH) plasma levels were also assessed. Force, sEMG and CK-LDH measurements were performed before EC and after it periodically for 4 weeks. The sEMG was analysed in time and frequency domains; a non-linear analysis (Lyapunov 1st exponent, L1) of sEMG was also performed. After EC, the MVC was reduced by 40% on average with respect to the pre-EC values. A significant decrease in the initial frequency content, and in the MDF and L1 decay (13-42% less than the pre-EC values, respectively) was also observed. The sEMG amplitude (Root Mean Square, RMS) was unchanged after EC. The US revealed an increase in muscle belly thickness and in local muscle blood flow after EC. A complete recovery of all the considered parameters was achieved in two weeks. In conclusion sEMG analysis was confirmed as an early indicator of muscle damage. Muscle recovery from damage is followed by both sEMG and US and this may have useful clinical implications. Non linear analysis (L1) was revealed to be sensitive to early sEMG modifications induced by EC as well as able to follow the post EC changes in the sEMG.

Adult↗
PubMed2001

ADAM-HCV, a new-concept diagnostic assay for antibodies to hepatitis C virus in serum.

We screened phage libraries using sera from noninfected individuals and patients infected by hepatitis C virus (HCV). By applying different selection and maturation strategies, we identified a wide collection of efficient phage-borne ligands for HCV-specific antibodies. The selected ligands retained their antigenic properties when expressed as multimeric synthetic peptides. Peptides that mimic several immunodominant epitopes of the virus were used to develop a novel type of diagnostic assay which efficiently detects antibodies to HCV in serum. This type of analysis provides a conclusive diagnosis for many patients identified as indeterminate according to presently available serological assays.

Amino Acid Sequence↗
PubMed2000

"Affinity maturation" of ligands for HCV-specific serum antibodies.

We have previously screened a phage-displayed random peptide library using sera from patients and identified ligands binding to antibodies specifically associated with the hepatitis C virus infection. The ability of these peptides to detect HCV-specific antibodies was improved through an in vitro procedure which mimics the natural process of antibody affinity maturation operating in secondary immune response. Libraries were generated by mutating the sequence of the original peptide through a protocol that efficiently introduced substitution, insertion and deletion mutations on a single or population of clones. Screening these libraries isolated mutants that displayed increased specific reactivity with a broader range of sera from HCV-infected patients. Several variants of the original peptide were identified which discriminate between the various components of the specific polyclonal response. This methodology to select artificial ligands from RPL using sera and to enhance their diagnostic properties by affinity maturation makes the development of a diagnostic assay to detect disease-associated antibodies feasible, without requiring the natural antigen.

Amino Acid Sequence↗
PubMed2000

Electromyogram changes during sustained contraction after resistance training in women in their 3rd and 8th decades.

The present study aimed at investigating the neuromuscular adaptations to 6 weeks of resistance training in women in their third (6 experimental, 8 controls) and eighth decades (8 experimental, 8 controls). The surface electromyogram (sEMG) was measured from the biceps brachii muscle during constant-force isometric contractions lasting 12 s at 80% of maximal voluntary contraction (MVC). All the signals were analysed adopting in the time domain the root mean square (RMS) as a measure of amplitude and in the frequency domain the median frequency (MDF) of the power spectrum. Quantitative analysis was performed from the 3rd to the 6th second, to describe the early phase of the contraction ("Early"), starting from point at which 80% of the MVC was reached, and from the 9th to the 12th second, to describe the last part of the constant-force sustained contraction ("Late"). After training, the MVC increased by 22.4% in the young (P < 0.0001) and by 13.4% in the older (P < 0.05) women. The "Early" RMS increased by 60.4% with respect to the pre-training condition in the young (P < 0.01) but not in the older women. In contrast, the "Late" RMS increased by 46.7% in the older (P < 0.05) but not in the young women. The MDF remained unchanged in both groups. These results indicate that young and older women showed different training-induced adaptation of the motor unit (MU) activation pattern, in order to keep a constant level of force during a sustained isometric contraction at 80% of MVC.

Adolescent↗
PubMed2000

Fallopian tube disease: the cobblestone pattern as a radiographic sign.

PURPOSE: To identify radiographic signs of mucosal damage by comparing hysterosalpingography with salpingoscopy in a prospective study. MATERIALS AND METHODS: Forty-one candidates for laparoscopy underwent hysterosalpingography and peroperative salpingoscopy; at both, tubal patency was noted. Radiographic criteria for mucosal abnormality were rounded filling defects (ie, the cobblestone pattern) and the absence of longitudinal radiolucent bands in the ampullary tract. At salpingoscopy, tubal mucosa was categorized by means of inspection into five classes of fold pattern: classes I and II, normal; classes III-V, abnormal. Hysterosalpingographic and salpingoscopic results were compared by means of a two-by-two table and kappa statistics. RESULTS: Seventy-four tubes were evaluated. At hysterosalpingography, 31 tubes were distally nonpatent. Of these, 26 showed a distal obstruction at salpingoscopy. None of the patent tubes at hysterosalpingography showed obstruction at salpingoscopy. The agreement between hysterosalpingography and salpingoscopy in detecting abnormal mucosal pattern was 89.2% (kappa, 0.73; P: <.001). The cobblestone pattern always corresponded to intraluminal adhesions at salpingoscopy. The absence of radiolucent bands corresponded to abnormal mucosa at salpingoscopy in four of six cases. The cobblestone pattern was found only in hydrosalpinges and never in patent tubes. Six normal patent tubes at hysterosalpingography showed intraluminal adhesions at salpingoscopy. CONCLUSION: Results indicate that the cobblestone pattern is an effective radiographic sign of intraluminal adhesions in hydrosalpinges and suggest that intraluminal disease in patent tubes might not always be excluded on normal hysterosalpingograms.

Adult↗
PubMed2000

'In vitro evolution' of ligands for HCV-specific serum antibodies.

We developed a strategy to improve the properties of ligands selected from phage-displayed random peptide libraries. A site-directed mutagenesis protocol that introduces mutations and extends the size of a target sequence has been set up to generate diversity in a single or in a population of clones. The pool of mutants thus created is screened to identify variants with the desired properties. We refer to this strategy as in vitro evolution' of ligands. Here we report the application of this in vitro evolution protocol to the identification of improved ligands for HCV-specific serum antibodies. A single clone or population of clones were processed to generate a secondary library. Screening of these libraries with sera from HCV-infected patients identified peptides with an enhanced and broadened ability to detect HCV-specific serum antibodies.

Antibodies, Viral↗
PubMed2000

Improvement of hysterosalpingographic accuracy in the diagnosis of peritubal adhesions.

OBJECTIVE: Our purpose was to compare hysterosalpingography with laparoscopy in the diagnosis of peritubal adhesions and to verify whether a combination of radiographic signs improves hysterosalpingographic accuracy. SUBJECTS AND METHODS: Thirty candidates for laparoscopy underwent hysterosalpingography before surgery. Two radiologists evaluated the presence or absence and types of radiographic signs of peritubal adhesions (convoluted tubes, vertical tubes, loculation of contrast medium in peritoneum, halo effect, and fixed laterodeviation of the uterus) using two different criteria for normality or abnormality: no sign means a normal result, one or more signs mean an abnormal result (first criterion); no sign or one sign means a normal result, two or more signs mean an abnormal result (second criterion). Interpretation discrepancies were resolved by consensus. Peritubal and periovarian adhesions were evaluated by a single operating surgeon during laparoscopy (recorded on S-VHS videotape) and by a different surgeon reviewing the videotape. The radiographic results obtained using the two criteria in radiologically patent as well as in distally nonpatent tubes were compared with corresponding laparoscopic results by 2 x 2 tables and were statistically analyzed (kappa statistics). RESULTS: The first criterion displayed poor diagnostic accuracy. The correlation with laparoscopy was not statistically significant in either radiologically patent or distally nonpatent tubes. The second criterion greatly improved the agreement with laparoscopy, but only in patent tubes (kappa = 0.7789; p<0.001). CONCLUSION: Hysterosalpingographic accuracy in peritubal adhesion diagnosis can be improved in patent tubes by taking into account more than one of the reported radiographic signs.

Adult↗
PubMed1999

Uptake and intracellular fate of phage display vectors in mammalian cells.

Receptor-mediated endocytosis is exploited in experimental systems for selective delivery of genes and drugs into specific cells. To improve targeting efficiency of delivery vectors, we have used phage display technology to isolate novel ligands for endocytosed receptors. We show here that phage vectors internalized by mammalian cells via integrin-mediated endocytosis can be rescued by cell lysis and quantitated by infection of bacteria. Immediately following uptake, phage enter an intracellular compartment where they remain intact, with phage titer unaffected by the addition of chloroquine. Phage are then translocated to a second intracellular compartment in which they are inactivated and their titer affected by chloroquine. Immunofluorescence microscopy showed an association of the second compartment with supranuclear organelles. The ability to recover internalized phage in an infectious form from two distinctive intracellular compartments provides a means to select novel ligands from phage libraries for targeted delivery of macromolecules into mammalian cells.

Amino Acid Sequence↗
PubMed1999

Targeted delivery of multivalent phage display vectors into mammalian cells.

Novel peptide motives targeting endocytosing receptors were isolated from phage display libraries of random peptides by recovering internalized phage from mammalian cells. The peptide-presenting phage selected by internalization in HEp-2 and ECV304 human cells were taken up 1000- to 100,000-fold more efficiently than their parent libraries, and from 10 to 100 times faster than phage particles displaying integrin-binding peptides. A high degree of selectivity of phage uptake was observed in these cells: phage selected in ECV304 cells were internalized approximately 100-fold more efficiently in ECV304 cells than in HEp-2 cells. Likewise, phage selected in HEp-2 cells were subsequently taken up approximately 40-fold more efficiently by HEp-2 cells than by ECV304 cells. In multiple independent trials using a cyclic peptide library, an identical peptide sequence displayed on phage was internalized by and recovered from ECV304 cells. These findings indicate that the internalization process is highly selective, and is capable of capturing a specific peptide from 2 x 10(7) peptide variants. Immunofluorescence microscopy showed juxtanuclear localization of internalized phage. These results demonstrate the feasibility of using multivalent phage-display libraries to identify new targeting ligands for the intracellular delivery of macromolecules.

Amino Acid Sequence↗